The first stage of management and SBS primarily focuses on TPN and managing fluid and electrolyte complications. Parenteral nutrition here differs very little from any disorder necessitating parenteral feeding. Baseline nutrient and energy needs must be met in a standard fashion. In children with SBS, fluid and electrolytes are often a challenge in the immediate postoperative period. Ongoing losses of fluid and substantial quantities of electrolytes are quite variable and highly dependent upon location of any ostomies in addition to losses from nasogastric, gastric, or naso-duodenal tubes. Gastric losses include significant volumes of hydrochloric acid and large quantities of potassium and sodium chloride which can affect acid–base balance as well as electrolyte losses. This hypersecretion of gastric acid and fluids may reduce pH below the optimal level needed for efficient fat absorption by inactivating pancreatic lipase and deconjugating bile salts requiring use of acid suppression. The gastric hypersecretion typically resolves in the first few months after surgery and is not required indefinitely. In fact, ongoing use, as in those without SBS, may be associated with increased risk of viral infections [9, 10].

Small bowel fluid losses contain much higher concentrations of sodium often approaching that of normal saline. Measurement of these ongoing losses and replacement with a solution separate from the TPN milliliter for milliliter are usually much simpler and preferable to constant reformulation of parenteral nutrition solution. Once ongoing losses stabilize, these volumes can be more easily incorporated into parenteral nutrition solution if desired.

The resting energy expenditure in infants with SBS is similar to healthy controls. However, because of malabsorption, the amount of energy needed will be greater (estimates of 30–70 % greater) than that needed parenterally to achieve similar weight gain [11, 12]. In general, growth is monitored by assessing whether increases in weight are proportional to linear growth. Factors such as genetics should also be factored into expectations for growth. Moreover, proportional growth does not necessarily avoid stunting , which appears to be common among children with SBS .

Patients on TPN should initially be monitored daily with electrolytes, blood urea nitrogen (BUN), creatinine, phosphorus, magnesium, albumin, triglycerides, and glucose then weekly until stable and with any subsequent change in TPN formulation or volume. Total and direct bilirubin and aminotransferases (aspartate aminotransferase, AST, and alanine transaminase, ALT) also should be measured regularly to monitor for parenteral–nutrition-associated liver disease. Monitoring of vitamin levels is not essential at this time but becomes of greater importance as the patient becomes solely dependent on enteral nutrition.

Once gastrointestinal motility resumes and the postoperative ileus has resolved, enteral nutrition can be judiciously initiated. Early initiation of enteral feeding is important for a number of reasons. Enteral nutrition has been shown to strengthen the mucosal barrier and reduce the risk of translocation of bacteria [13]. In addition, the adaptation process which is crucial to long-term survival without parenteral nutrition or at least with minimal parenteral nutrition does not occur in the absence of enteral feeding. Aggressive use of enteral feeding, especially early in the course of treatment, significantly enhances the adaptation process [14]. Much work has been done to understand the role of enteral nutrition, and we do know that certain nutrients appear to be more important than others. Long-chain fats, especially three omega fatty acids, at least eicosapentaenoic acid, appear to be very important in this process [15]. Consequently, making sure a significant portion of enteral feeding is in the formal long-chain fats is advantageous. More important, however, is the use of aggressive enteral nutrition as early as possible after resection.

Selection of the appropriate enteral feeding solution is dependent upon a number of factors. In small infants, hydrolyzed or elemental formulations are commonly utilized. There are substantial data however suggesting that human milk may provide an excellent alternative [16]. Human milk, especially when fresh, contains a number of trophic factors not commonly present in predigested formula is. Predigested formulas are commonly used because the nutrients provided are in a form ready for absorption. This avoids wasting part of the absorptive surface while digestion is occurring. Although osmolality is often utilized as a reason to avoid predigested formulas, this is really an issue only when continuous enteral infusion is not being employed. Hyperosmolar formulas of any type when administered via a slow continuous tube feeding are well tolerated. If used, elemental formulas should contain at least 40 % of their calories as fat. Some data suggest that more complex formulations may be advantageous for adaptation, due to a greater functional workload demanded from the small-bowel epithelium [16, 17]. In practicality, most clinicians avoid whole protein formulas, as there is an increased risk of non-IgE allergic injury from an intact proteins especially true during the first 2 years of life [17, 18].

The use of medium-chain triglycerides is comparably controversial. While medium-chain triglycerides are better absorbed especially when the supply of pancreatic enzymes or bile acids are limited, they are also less trophic to the small bowel. Medium chain fats also have a lower energy density and exert a greater osmotic load on the epithelium than long chain fats. The optimal ratio between long- and medium-chain fats has not yet been identified, but a majority of the fat delivered early in the course of enteral feeding should probably be supplied in the form of long-chain fats. Pancreatic insufficiency is rarely a problem in these patients, and bile acid deficiency is usually only an issue in infants with liver disease or massive ileal resection.

The ratio of calories provided between fat and carbohydrate is also arguable. The coefficient of absorption of carbohydrate is better, but the caloric density of fat is much higher. Carbohydrate is the preferred nutritional substrate for bacteria and favors the development of small-bowel bacterial overgrowth, another major complication of SBS. Formulations higher in fat and lower in carbohydrate work better in infants with SBS when the risk of injury from small-bowel bacterial overgrowth is potentially higher [19]. In adults, or older children, colonic salvage of short-chain fatty acids and reduced by bacterial metabolism from malabsorbed carbohydrate is much better which is probably why older children and adults do somewhat better than small infants with a higher proportion of carbohydrate in their enteral feeding. Lactose restriction is not required as most is absorbed in the proximal bowel which is often preserved in many cases of pediatric SBS.

Fiber supplementation may be beneficial not only in absorbing some of the water losses but also provide an additional energy source in patients with a retained colon. In older children, significant malabsorption of fat may lead to oxalate absorption due to the loss of calcium and subsequent development of hyperoxaluria and the formation of kidney stones.

Once initiated, enteral feedings are gradually increased as tolerated. Feeding 24 h a day will optimize absorption through continuous use of the available gut mucosa. The rate of infusion can be gradually increased based on tolerance. Ostomy output in excess of 30–50 mL/kg per day is usually a contraindication to advancing feedings. Measuring reducing substances in the stool or ostomy output will also provide a clue as to whether or not the absorptive threshold has been reached. Once carbohydrate malabsorption begins, advancing feedings usually precipitates more osmotic fluid loss. As the tolerance to enteral feeding increases, parenteral nutrition is reduced in an isocaloric fashion. During this time, the patient has often been weaned to receiving parenteral nutrition during only part of the day or night with the infusion device capped for a certain number of hours each day. The length of the time off of parenteral nutrition can gradually be increased to facilitate care and mobility the patient, rather than simply decreasing the parenteral nutrition rate. Eventually, as enteral nutrition tolerance increases, the patient’s parenteral nutrition may be deleted for one night a week, then two, and progressed until the patient is no longer receiving parenteral nutrition.

Enteral nutrition can be provided orally through bolus feedings or by continuous enteral infusion. Oral nutrition has the advantage of including the oral and cephalic processes of digestion and absorption which might perhaps play a role in adaptation. However, especially in small children or infants, continuous enteral infusion is usually employed. Continuous enteral infusion provides constant stimulation for mucosal adaptation. As the nutrients are introduced more slowly and continuously into the gut, optimal saturation of transport carriers is achieved. The enhanced absorption thereby reduces the need of parenteral calories which likewise reduces the risk of parenteral-nutrition-induced liver disease, one of the most common morbidities seen in SBS.

It is extremely important to initiate small quantities of oral bolus feeding early in the course of therapy. Especially in small infants, if this is not done, oral food aversion becomes a real problem. If only a few milliliters of formula or human milk are given through by mouth four times per day, the risk of oral food aversion can be significantly reduced. Solid foods can be initiated at the usual time (4–6 months of age) in small quantities despite the fact that the child continues to receive most of their enteral nutrition through a continuous infusion. The choice of solid food feeding is also open to controversy. Although it is customary in many cultures to begin oral feedings with carbohydrates such as cereal, there is little logic to this practice. Meat is probably an ideal first food for the short-bowel patient. Meat is high in fat and protein which are both important in stimulating mucosal adaptation and contain little or no carbohydrate which could increase osmotic fluid losses and small bowel bacterial overgrowth.

As feedings are progressed, the short-bowel patient may be receiving solids and oral bolus feedings during the daytime and continuous enteral infusion at night. This also permits optimal use of the gut. Nighttime enteral nutrition however frequently reduces the appetite in the morning and sometimes needs to be reduced to encourage the child to eat. A careful balance among all of these various factors requires clinical experience. This is perhaps one of the reasons why a multidisciplinary approach in SBS has been so successful in major centers [20].

In the management of older children was SBS, oral nutrition is often advanced more quickly. In this instance, the use of small frequent feedings every 2–3 h is beneficial over larger less frequent feedings as it more closely mimics the advantage of continuous enteral infusion [21]. Here, the selection of foods is very important. It is important that each meal contains a balance of carbohydrate, fat, and protein to avoid overloading the small intestinal capacity to absorb micronutrients. An equal balance between carbohydrate and fat, and a significant amount of protein in each of several small meals during the day, will not only facilitate adaptation but also reduce the risk of malabsorption and excessive fluid losses. Involvement of nutritionists who understand this principal and can counsel and educate the patient well is very important at this stage. A nice example is the concept of a small sandwich as the proper size of meal. The bread is the carbohydrate, the meat is the protein, and the butter is the fat. If this counseling is not provided, the patient may well choose to eat small meals but will consume all carbohydrate in one meal and all protein in the next because this is often easier to provide. The major risk in oral feeding is the consumption of large carbohydrate-containing meals. Carbohydrate, even in the form of disaccharides, is rapidly digested in the small bowel creating an osmotic load which results in fluid rushing into the lumen creating diarrhea or large-volume ostomy losses. Simple carbohydrates are even more problematic. Including fat and protein in each meal while reducing the amount of carbohydrate reduces this risk significantly.